optrees (version 1.0)

checkGraph: Checks if the graph contains at least one tree or one arborescence

Description

The checkGraph function checks if it is possible to find at least one tree (or arborescence, if it is the case) in the graph. It only happens when the graph is connected and it is posible to find a walk from the source to any other node.

Usage

checkGraph(nodes, arcs, source.node = 1, directed = TRUE)

Arguments

nodes

vector containing the nodes of the graph, identified by a number that goes from $1$ to the order of the graph.

arcs

matrix with the list of arcs of the graph. Each row represents one arc. The first two columns contain the two endpoints of each arc and the third column contains their weights.

source.node

number pointing the source node of the graph.

directed

logical value indicating whether the graph is directed (TRUE) or not (FALSE).

Value

checkGraph returns the value TRUE if the graph meets the requirements and FALSE otherwise. If the graph is not acceptable this functions also prints the reason.

Examples

# Graph
nodes <- 1:4
arcs <- matrix(c(1,2,2, 1,3,15, 2,3,1, 2,4,9, 3,4,1),
               byrow = TRUE, ncol = 3)
# Check graph
checkGraph(nodes, arcs)

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